Metal vapor condensation



May 9, 1944- R. G. CRANE ETAL 2,348,194

METAL VAPOR CONDENSATION Filed June 5, 1942 hi n f i W5S;

Il @w l l| f! I I l w QI gm l\ l il; I l f INVENTOR ioland rane BYMelville Per/fia.;

lPutente'l'l May9, I l Y w condenser and vmethod of condensing zinc 0,Whi ch is supDOrted horizontally .on roller.

Marax. varon coNnENsArroN y f Roland G.V Crane, .-Woodbrid'ge, andMelville L/ff Perkins, Barber, Nfl., assixnorato American Smelting and'Refining Company. New York, z N. Y.; a corporation olNcw J rsey f'Application June l3, 1a4z,l'seri'a1i\i. 445,514 I 'sclaims. fletes-:14)a l Thisinvention relates to the metallurgy` of.,l I' denseryasillustrated in Figure.V 1, consists o faf zinc and more particularly toan improved .hollow cylindrical member,generallydesignated UNITEDAs'A-TAE'S 1PA-rear vapors formed by smelting zinc containing submeans-l I.' `Duringthe processing treatment, the' stances. The inventionis adapted for use with- 5- condenser is rotated.- .Mechanism suitablefor any of the conventionalfurnaces but is espe#V eiectingthisis showninFlgure 1 andcomprisesf cially useful in condensingmetal vaporsjfromaringjgeariz which-is' attached to the-condenelectric arc smeltingfurnaces.` I se'r and arranged to` be driven A-by` afmotor I3` In therecovery of metallic zinc by thermal through' theinterconnecting chain-means M, l reduction ofzincy substances 'with carbonace' jl0 "Hot metal`Vaporsare conductedfromy a -smeltous reducing agents, zinc is vaporizedand conf- V ing furnace'generally designatedat- I5 into fthe? ducted toa condenser whereitis condensed tof con'clen'serflty"15s/ ay of theconduit I6.. 'I his con# liquid metal. Many different types ofcondensersf duit is preferablymade ofrre'fractory material; and smeltingarrangements have vbeen proposed andforms'fan extension ofthe-furnaceilue I 1." heretofore, including` rotary devices, but suolil5 Toform a gas'tight connectionbetween the devices have been primarilydesigned and used Ato outer end of the conduit IB andthe condenser.recover metallic zinc from blue -powder..- f the x'n`e' mbe'r I6 is-telescopicallynt 'into the ther, prior to our invention, in' spite 'or'all iprecylindrical f vextension I8 of the condenser, -as' l cautions,it has been practically impossibleV to shown in Figure 1.` l Asbestospacking'-is corn-4 condense metal vapors, such as zinc, from an'arc. 20pressed-into the space between the outer walli furnace withoutformingjexcessive amounts of of the conduitl andthecircumjacentextension blue powder which requires resmelting or special JI 8 offthe condenser and isljleld` inplace by,I a treatment for therecovery -ofits metallic zinc retaining ringflnemberfzz. Suiijztblevmeansis", content. a also'. pro vi ded` -for '-1 'I lowing cooling;Water over It isv the principal object of this invention to 25' theouter surface o'ffthe memberlikasfillus-fI overcomethese dllcultiesandprovide af con-1v tratedfin Figure 1,-.tfo improvethe'sealjbetweendenser and method of treating `zinc vapors wherel C the` parts graphitedisc 2l of' suitable 'thick- -i by they can be condensed vdirectly tometallic nessisinterposedbetweenthe outerend'ofthefg, zinc Whileavoiding the formation: of a high, Jjonduitfl'and the condensertoassistin forming. ,1 proportion of'blue powder.`l 3 0"agastight" jointfAnother object is to providev an improve'dro- -condIlSr 'f'comprisesv`'armetal shell-25? tary condenser whicnis' operable to eiectsub- :fhavingv At 1'1e' jen iiclosing,plates-'21." The shell-isi: stantiallyinstantaneous 'condensation o f the equippedfwith tiresli'orengaging the'supportmetal vapors upon enteringthecondenser-.f2 v. ingrollerfmeansujI'jduringfrotation ofth 'con= Another object is to devisea' method iofcool- :zadensen-jrlofprftyfhf metaf she11,-- i|j 1s'=1inediing zinc metalvapors as-emittedfrorn'- en -arc: gmconcalrbideor smeltingfurnace with ysuch rapidity that oxif th- 'jike' maf-,gal,whfhsbgtaau'y. `in; dation of thezinc to form'bluepowder in appermebilgt:thfmtlvpo-S.beigcodensei preciable amountsis avoidet'l-v v ui Wherefurther-'protection i".-z d`e'sired, al'ay'er of. f; otherObJectS and advantages ofthe inventien 4!! micaor' asbesto'rs not shown;may be placed m E Wm become apparent fffelihe follpwng'detiled:afweer-1. usf 'Quiet nie-ar steunend-stas fe: f l lrpti vtfin-cn-'z-cion' mhp??? a?" .frefforrfl-1inms,e2.iA bafhfof P601.'efrliquid' p ny g g"1 W 1 metal- 3551smamtameazmtneiower portion o'ftionof a condenser. constructed'in accordance; l f, f. -1 with the'presentinvention, the condenser being denser'fliguid ,metalli-s'-cgminuauyfsplas'hd' shown connected toan arc smelting furnacefnfted-and-hurled ffom'tthebg'thmtothgspa which is illustrateddiagrammatically andshown ftherapoye''produmg anatmospher med withpartly broken away; Y 1 mvmg, droplesy'finqud'f-metal ITO.. pr`` Figure2-is avertical cross-sectional view taken; lit)y Vide, means for:acgmpnshmgimsf the' Gln-:ula: substantially on the line 2-2 of- Figure1:7; Sid? Wan-@f thefondnser L1 5 m9419119 of spaced Figure 3 is anenlarged perspective .view of I'WS 0 5 bamelblQQkS .fajuwhch'ldwShped`-t9 I we f the bames which are shaped tothe 'fitted f splash anddip up- 11qu1.d"mew1fromthebotwm together to form a lining for the.condenser.' part of the condenser as it ls-rotated Referring to thedrawing in detail, the cpud6, The cames'-arelcnstructedffromggrdradbymaterial, shaped and fitted together. as illustrated in Figures 2 and 3,to form a substantially continuous limer wall. 'Ihis baille wallconstruction preferably extends throughout the entire length of thecondenser inasmuch as we have found by-tests that where the condenser ismade up oi' plain unbamed sections the resultant emciency of the'condenser is lowered. Each baille member qomprises a shoulder orabutment 4l which protrudes inwardly and is inclined to the curvedbacking wall portion l2. Tongue and groove sections 4I and Ilrespectively are provided at the opposite ends of the curbed backingportions to form tight joints between the bane blocks.A An elongatedcupor trough I8 is formed on the outer sloping side of the abutment part 4Iof each baille which, during rotation of the condenser, is vfilled withliquid metal from the pool 36. In this manner, as the condenser rotates,liquid metal is picked up from the bath and carried into the upper partof the condenser where the metal is discharged producing a series ofliquid metal cascades to which the incoming hot metal vapor issubjected.

To eliminate end-to-end surging of the metal bath resulting in excessivedischarge of, `liquid metal therefrom w hich would lower the eiliciencyof the process, the inner end wall sections of the condenser arecorbelled, as shown at 4l in Figure 1. This improved constructionefi'ectively inhibits surging of the liquid metal bath permitting thecondenser to be rotated at high speed while the amount of the liquidmetal in the bath remains substantially constant.

Heat is dissipated rapidly by our rotary condenser arrangement, so that,in most installations, it is necessary to supply heat to the exterior ofthe condenser -to maintain the liquid metal bath at the propertemperatin'e. Suitable means may be provided for supplying heat, such asby the use of a burner, as shown at Il. Where the temperature ofthemetal vapors entering the condenser is such as to require cooling of thecondenser, conventional means such as shown at Il, may be utilized inplace of the burner for inches and a length of seven feet was directlyconnected to la top-arc smelting furnace. The condenser which waspartially filled with liquid 'metal zinc was rotated at a speed of 45 R.P. M. Approximately 1600 pounds of zinc metal was recovered per dayusing a charge assaying about 60% zinc. This charge consisted of amixture by weight of 100 parts brass furnace dust calcined and screenedto -5/4". 16 parts coke of and 5 parts calcareous slag material.Suflicient heat was supplied to maintain the liquid metal bath at about500 C. Metal vapor at a temperature of around 1000 C. was condensed withabout 6 to 12% of the zinc entering the condenser emerging in the formof blue powder. This represents a decided improvement over resultsattained heretofore using the conventional conapplying a spray of wateror the like coolingv j medium to the outer walls of the condenser.

In smelting zinc `materials in an arc furnace. there is a tendency formany compounds of moderately low vapor pressure, such as PbC, PbS, SnO,ZnO and the like, to volatilize in the intense heat of the arc. The morereducible of these are immediately acted upon by the hot metal vaporsand by carbon monoxide Awith the resultant formation, either directly orindirectly, yof C02. The carbon dioxide gas which does not Example Acondenser, constructed as illustrated and described, having an insidediameter' of twenty densing mechanism wherein from 30 to 75% of the zincis recovered as blue powder.

To initiate the process, the condenser is heated to around 500 C. andthe lower part of the condenser is filled with molten zinc 36. As metalvapor passes into the condenser and is recovered as liquid metalincreasing the size of the metal bath 36, a like amount is drawn of!through the openingv 52 or is intermittently tapped from the condenser.During the process the lcondenser is continuously rotated at asubstantially coxfstant R. P. M. Preferably, the condenser is rotated atbetween and 5 4, of the critical rotational speed or that at which theliquid metal would centrifuge. This critical rotational speed for anygiven size rotary drum-like member has been authoritatively representedby the following formula:

54.19 1/ Internal radius of the drum in feet Rotation of the condenserat this relatively high lspeed during the process has been found to be asalient factor in obtaining the improved results. The metal vapors whichleave the arc furnace at a temperature of about 1100" C. enter thecondenser at considerable velocity and are forced to take a twisting,spirally extended path therethrough. Intimate intermixing of the va`pors with liquid metal zinc at a temperature below the dew point of themetal vapor is effected by subjecting the vapor to a torrential showerof liquid zinc falling in cascades from the top portion of thecondenser. This enveloping and uniform intermixing of the metal vaporphase with the liquid zinc combined with the vigorous splashing andsloshing created by the bailles travelling into and out of the pool ofmetal in the lower part of the condenser, produces an intense scrubbingaction on the metal vapors and mechanically disrupts the metalcondensate fllms on the droplets of zinc causing the same to coalesce toliquid zinc and decreasing to a minimum the metallic zinc content of thesmall amount of blue powder formed. In order to secure the best results,it is necessary that suiiicient amount of liquid-metal zinc is kept inthe condenser so that the maximum effect of the moving. bales can beobtained at all times.

Although the improved condenser and method is particularly useful inconnection with the production' of zinc metal, it will be obvious thatthe invention may be advantageously employed to condense other metalvapors, such as magnesium and the like, toliquid metal form as well asvapors comprising a mixture of different metals for example, lead, zinc,tin, etc.

While the preferred form of apparatus and method of practicing theinvention has been described in detail, it is to be understood that theprocedure and form of condenser may be modified by those skilled in theart without departing from the spirit and scope of the invention asdefined by the appended claims.

What is claimed is:

1. An improved condenser for condensing zinc metal vapors formed in anelectric arc smelting furnace comprising a rotatable chamber into whichthe hot metal vapors from the furnace are conducted, means for rotatingsaid chamber, a bath of liquid zinc metal lling the lower portion ofsaid chamber, means comprising spaced interlocked baille blocks formingthe inner wall of said rotating member for splashing and hurling liquidmetal from said bath into the space thereabove to maintain the samefilled with falling droplets of liquid zinc metal and to produce anintense scrubbing and substantially instantaneousquenching action on themetal vapors upon their entry into said chamber, said chamber havingcorbelled end-wall sections to inhibit endto-end surging and prematuredischarge of liquid metal from said bath as said chamber is rotated.

2. In the art of producing zinc by reducing zinc bearing substances inan electric arc furnace and condensing the metal vapors emittedtherefrom,`

that improvement which consists in directly subj`ecting the zinc vaporfrom the reduction operation without intermediate conditioning treatmentto substantially instantaneous quenching by intimately intermixing saidzinc vapor with a torrential shower of moving droplets of liquid zincwhile intimately contacting it with a vigorously agitated bath of liquidzinc.

3. The process of producing zinc which consists in heating a chargecomprising zinc containing material and carbonaceous reducing agent inan electric arc furnace, conducting the zinc vapors formed in the arcfurnace directly withoutintermediate treatment into a rotary condensercomprising a cooling shower of liquid zinc which is maintained over abath ofl liquid zinc metal to thereby quench the zinc vapor and condensethe same to liquid zinc metal without ap-v 4. The process of cooling andcondensingzlnc Vmetal vapor at a temperature of approximately vaporintoa chamber lled with moving droplets l of molten liquid zinc maintainedover a bath of liquid zinc metal contained in said chamber, andsubjecting said droplets to attrition by intimately contacting the samewith said bath of liquid zinc while it is vigorously agitated to therebymechanically disrupt the films formed on the droplets to recover zinc asliquid metal and controlling the temperature of said molten zinc so asto quickly absorb the heat of condensation whereby the zinc vapor iscondensed to the liquid phase in such a short period of time thatoxidation of the zinc to form 'substantial amounts of blue powder isinhibited.

5. An improved condenser for condensing zinc vapors formed in anelectric arc smelting furnace to liquid zinc metal comprising a rotarychamber into which hot zinc metal vapors are introduced directly fromsaid arc furnace, said chamber being adapted to contain a bath of liquidzinc in the lower portion thereof, spaced inner baflle wall meansprotruding inwardly and extending substantially throughout the length ofsaid chamber, said baffle means having an integral backing wall which iscurved to flt the circular wall of the chamber, said backing walls beinginterlocked in such a manner to form a continuous lining wall for saidchamber, mean for rotating said chamber at a relatively high uniformrotational speed to cause portions of the liquid zinc to be picked upfrom the bath and carried to the uppermost part of the rotating chamberby said baille wall means and.cascaded through said zinc metal vapors inthe form of droplets as said vapors are conductedv into said chamber,

said zinc vapors being cooled to the dew point with such rapidity thatoxidation of the zinc to form blue powder in appreciable amounts isavoided, said chamber having corbelled end-wall sections to inhibitend-to-end surging and premature discharge of liquid metal from saidbath as said chamber is rotated.

RCLAND G. CRANE. MELVILLE F. PERKINS.

